Wraparound gear mechanisms are known from the prior art, by way of which an infinitely variable change in the step-up transmission ratio (or step-down transmission ratio) is possible at least within ranges. To this end, two cone pulley pairs are provided that have in each case two cone pulleys. The cone pulleys are oriented in each case with their cone face toward one another and can be displaced along their common rotational axis relative to one another between a position at a maximum spacing and a position at a minimum spacing. One cone pulley is usually fixed axially and the other cone pulley can be displaced axially. In this way, a pulley wedge which is variable is formed between the cone pulleys of a cone pulley pair. The two cone pulley pairs are connected to one another in a torque-transmitting manner by means of a common wraparound means, for example a transmission chain. The wraparound means migrates radially to the outside in a cone pulley pair when the cone pulleys thereof are guided toward one another, and the wraparound means migrates radially to the inside in a cone pulley pair when the cone pulley pairs are moved apart from one another. Said movement is as a rule carried out in each case precisely in the opposite manner in a wraparound gear mechanism on the cone pulley pairs, with the result that the tensioning of the wraparound means remains (virtually) constant, while the spacing between the cone pulley pairs is fixed, and it not being necessary for a deflection mechanism or tensioning mechanism to be provided for the wraparound means.
A transmission input shaft is fixed rotationally relative to a first cone pulley pair, and a transmission output shaft is fixed rotationally relative to a second cone pulley pair which is connected in a torque-transmitting manner by means of the wraparound means. A step-up transmission ratio can be set depending on the selected spacing of the cone pulleys of a cone pulley pair from one another in relation to the selected spacing of the other cone pulley pair.
A wraparound gear mechanism of this type is known, for example, from DE 100 17 005 A1. In some fields of application, the wraparound gear mechanism is combined with a conventional manual transmission with fixed transmission gears, with the result that a greater step-up transmission ratio spread is achieved with a comparatively lower number of fixed transmission gears.
On account of the fact that the wraparound means leaves the pulley wedge which is formed between the cone pulleys of a cone pulley pair in a manner which is not tangential with respect to the connection, in particular on account of polygonal running which results from a “usually” finite pitch of a chain, and other dynamic effects while running into and running out of the pulley wedge and as a consequence of changes in the step-up transmission ratio and/or as a consequence of rotational non-uniformities and other vibrations, the wraparound means is set in vibration about the wraparound means plane. The wraparound means plane (or vibration plane for short) is the shortest tangential connection of the set effective radius of the cone pulley pairs, that is to say the spacing of the truncated pulley wedge which is formed between the cone pulleys and corresponds to the width of the wraparound means. The position of the vibration plane is therefore variable with the change in the step-up transmission ratio. The vibration plane is as a rule congruent with the center plane in the running direction of the respective run, that is to say the pulling run (or load run) or the empty run of the wraparound means. In order to reduce said vibrations, sliding rails are used in the prior art which bear against the wraparound means with as little play as possible over as long an extent as possible and thus suppress vibrations and undulations of the wraparound means. Sliding rails of this type are known, for example, from the abovementioned DE 100 17 005 A1.
It is advantageous for many applications to construct the sliding rail in two pieces, it being possible for the two sliding rail halves to be pushed over the wraparound means laterally, that is to say in the axial direction of the wraparound gear mechanism, and to subsequently be connected to one another. A sliding rail of this type is known, for example, from DE 10 2013 211 748 A1. It has been determined surprisingly, however, that faulty connections can occur during the assembly of a two-piece sliding rail of this type.